In general, a steel manufacturing process includes an iron-making process of manufacturing liquid steel, a steel-making process of removing impurities from the liquid steel, a continuous casting process of casting the liquid steel into solid steel, and a rolling process of rolling the solid steel into a steel sheet or wire. The rolling process refers to a process of passing an intermediate material such as slab or bloom, manufactured during the continuous casting process, between a plurality of rotating rollers and applying a continuous force to enlarge or thin the intermediate material. The rolling process is roughly divided into a hot rolling process and a cold rolling process.
The above-described configuration is a related art for helping an understanding of the present invention, and does not mean a related art which is widely known in the technical field to which the present invention pertains.